Foil adhesive system



inch.

1,983,641- iron. SYSTEM David L. McConaughy, Penn Township, Allegheny it a e P te County, Pa.,assignor, by mesne assignments, to American-Marletta Company, Stoner-Mudge Co. Division, Chicago, 11]., a corporation of Illinois This invention relates to the heat sealing of adhesive between metal foil, to the resultant laminate, and ,to the adhesive composition therefor, andhas particular application to aluminum foil which is wrapped around food items smallfmachineryparts, and the like, and isthenj sealed "by applying heat and pressure to bond adhesive which has been coated between superimposed layers of the foil.

It is customary to coat foil for such purposes with an wound in rolls, and thereafter is usually shipped and stored before being'unwound and used to package various articles The packaging operation usually involves cutting the foil into separate sheets, sandwiching the articles to be packaged between two sheets, with their adhesive-coated areas facing each other, and applying 1 heat and pressure to the overlapping edges as the sheets until the adhesive bonds the sheets together Such bonding is usually accomplished by applying pressure of about 20 to about 60 pounds per square inch at a ,platen temrperature of about 200 Frto about 400 F for about 1 to about lOseconds The amount of pressure is not critical," andthe temperature varies inversely with the time p Various some of the vinyl resins give useful results However, unmodified vinyl adhesive compositions require relatively high sealing temperatures (over about 225 F. platen temperature at 5 seconds) to achieve a good bon dpand using a plasticizer to modify the vinyl adhesive composi adhesives have been tried for the purpose, and.

tion to lower its bonding temperature has the unfortunate effect of tending to cause "a premature bond, known as blocking, ratutemperatures of aboutlZO to about 130 F. at pressures of about 0.5 to about 1.0 pound per square In accordaiice with the present invention a foil adhesive is provided 'which is usable in presently standard fi nmt qial aaek n v equ pm to g r stronger bond, and improved resistance to blocking.

The composition of the invention has as its essential components (1) a resin which ispadhesive under heat a and. pressure ofabout 200 at aboutw20 pounds per square inch, (23 a plasticizer tor the resin, and (3) inert particles In' addition to these componentsgavolatile the-composition forpui'pose of facilitating the coating of the composition 9n the toil i After thecompositionhas been appliedto the foil, it is baked at about 400 F. to

aboutSQO" F; for about 1'0 touabout 15 seconds, in order to drive bfli the solventsbefojre the coated toil is woundr 91. 5, F r wir se flot th invention, th P a portion of-the resin component ranges from about:

to about of the combined weight oftheresin and plasticizer components, the halance being the plasticizer, and the proportio'otthe'oomponentof inerh'particle v 13 9% 7 or thecombined V60 organicsfolvent is preferably used to' reduce viscosity of a 2 t y L weight of the resin, plasticizer and inertwparticle com:- ponents. l I T The resin component of the composition of the invention has as its essential constituennone or a mixture of oopolymers of (l) a vinyl halide, preferably vinyl chloride; (2) a vinyl tester ofa lower saturated fatty acid, preferably vinyl acetate; and (3) an aliphatic alpha, betamono-olefinic carboxylic acid, preferably maleic acid, the amount of carboxylic acid combined in the copolymer bein-gbetween about 0. 1% to -about 4% by weight of the whole copolymer, and the carboxyl groups in the copolymer being substantially unreacted. The optimum amount of maleic acid, when it is used as thelthirdcomponent of the copolymer, is about 0.3% to about 3% by weight of the total copolymer. The proportion of the vinyl halide component (1) in the copolymer isin-the range fof about 60% to about by weight of the total .copolymer, the balance being the said components (2) and (3) of the copolymer. The present preferred example of the essential constituent of the resin com.- ponent is a copolymer of vinyl chloride, vinyl acetate and. maleic acid in proportions by weight of about 86/ 13/1, as exemplified by VMCH of Bakelite Company, Union Carbide and Carbon Corp, of New York,

: Theresin component of the composition of the invention consists of between about 50% by weight to by Weight of the above-described essential constituent copolymer, the balance being one or more other vinyl polymers or copplymers which are compatible with said essential constituent, as evidenced by clarity of a solution of the mixed resin component. Copolyrners of vinyl chloride and vinyl acetate are suitable for such compatible mixtures; e.g., copolymers of vinylchloride and vinylacetate in proportions by Weight of 87/13, which are exemplified by VYL and the higher molecular weight VYHH, both of Bakelite Company, Union Carbide and Carbon Corp.. New York, N.Y. When the proportion of the essential constituent is about 50% or more by weighttof the total resin componenn the characteristics of the composition are not adversely afiected to any significant de'gree. Since the essential constituent is relatively expensive, a resin component consisting of-equal partsiby weight of the essential constituent and the compatible constituent represents an-optimum balance of performance and economy. 7 p

The plasticizer componentof the composition oftthe inventionisany plasticizer for the resin component which boils above 200 :C., andjis =fluid at about ZSQC; (average room temperature). Such plasticizers areknown in the ;art, and includezone or a mixture of organic acid esters having suchyboiling and fluid characteristics; e.g., esters of phthalic acid such as di (2 ethyl hexyl) phthalate, di butoxyethyl phthalate and di ethoxyethyl phthalate; esters of adipic acid such as di butoxyethyl adipate and di met-hylcyclohexyl adipate; esters, of s'ebacic acid such as di methoxyet hyl sebacate; and esters of sulfonic acids such as, o-cresyl p-toluene rsulfonate y, these plasticizers, di (2 ethyl heriyl) phthalate a nd "toluene sulfonate are piesently preferred. 5 a p g The inert particles component of, the,composition ff the invention is one or 'a mixture of materials lwhichare sre l P;-

non-reactive withthe resin and plasticizer components,

which are notsoftened by thefplasticizer component,

which are insoluble in the organicysolvents used with the bonding successivepairs of 11inch wide foil strips tov gether, under thestated conditions, along their mid-porthe adjacent free end of'the other strip, sufficient to pull .bf i esistaiiee td ration York, N.Y.), diatomaceous earth, china clay, slate flour, Tables .1], .III and IV. are basedon similartests, as

talc or carbon. follows:

The solvent used to reduce viscosity of the composi- TABLE II tion- -for purposes-of applying it -to the 'foil is not critical f mimosa f the inventiontand may be lr ted fi Efiect of varymg proportions of men particles m the various active volatile Y organic solvents :known in the l art compost'on for-usewith tlie resincomponent ozt the invention; e.'g. ketonefsolvents-such as-methylcthyl ketone (preferred), Examples and-methyl isobut-yl ketone,'a'nd ether alcohols, such as fCellosolve of "Union Carbide and Carbon Corp of F New York, NY; These active "solvents may be used singly "or mixed, and may be-used in conjunction with 00111111511611 g g figaf one-or a mixture of lessactive solvent'diluents, such as E Z( %S TI ;T 7g 70 4 7 p 70; 270,5 70 benzene, toluene and xylene. The solvent should be m y capable of being volatilized 'and'baked out of the comhem) phthamte)"m 3O 30 30 30 (3) Iuert particles (5 tOcelO position in about 10 seconds at about 400 F. Required platen temp in 1 Other materials, such as waxes, dyes and thermal grees F. for bonding in 5 I stabilizers, may be used in the composition of the inseconds 40 PM 150 175 225 Bond strength (pounds/inch v" I.

vention, as additives or modifiers, as will be understood width 1 00 2 09 2.64 2.21 2-50 2.00

vention i suitable for bonding at a platen temperature blocklng): j I 6 5 9 975: of about150to about 500 F. for about second to ggggfigjgfgflffi-z: 8 5 7 1o about 10 seconds, the time generally varying inversely with-the temperature. J I

The following Table I illustrates by examples the effect TABLE HI 7 of varying the proportions of the three essential comp 7 ponents of the invention. In each of the examples in Efiecrof difierent-species'of i rt ert particles Table I, the resin was a copolymer of vinyl chloride, 1 c 1 vinyl acetate and maleic acid copolymer in proportions 'Example's of about 86/13/1 (VMCH), the plasticizer was di V r j I (2 ethyl hexyl) phthalate, and the non-reactive particles z B 'L N component was silica aerogel (Santocel C). These L components were dispersed in methyl ethyl ketone and Components of adhesive c'om- Y ositlon (parts'by weight); r

were thoroughly intermixed 1n a dispersion mill. The P (D Resin 80 8O 80;

resultant mixture was thmned with additional methyl 2 Plasticizer (di (2 ethyl I 45-55 Krebs units at 77 F. (about 38% solids content s Parts; 0 s (05" .Y speci'es 1.--; v 1 a m the mixture), and was applled to aluminum foil and Require/513mm temp in i 1 M I V baked for 10 seconds at 400 F., the final coating weight 40 grees F. for bending in -5 I being approximately 2 milligrams per square inch. secmds at 195 2 l 9 width).. .L 1170- 1.37 use a-aa 1:68 2.47

. TABLE I Blockiulgtreiilstallttce (sgglebof 0, i I.

Efiect of presence of plastzclzer and mert particles, In the i blockmg): I V I I t I r (a) Ooatmg-to-coatlng 4 9.5. i c p (b) G0ating-t0-foil .4 k 10 Examples 1 Silica Gel. v V 'China Clay. 1 v

v I *SantocelG. m A. B .0 D p G 4 Activated carbon. H H i j Bentone34 H 'C omp'o nentsof adhesive composition. V i A; j p TABLE IV v ifi ri i iziiton h 100 so 90 95 7 0 A d l V i I esm u 7 H I e t I (2) l l t fi l t (2 ethyl hexyl) 0 2 z 0 30 I Eflect of zfier nt species of pest zctzers Required platen temp. in degrees F. p v v x m l for bondiug'in 5 seconds at 40 p-.;s.i 225 160 225' 233 '171 Bond strength (pounds/inch width)--. 0.80 1. 70 1.31. 0.70 2.04 1

Blocking resistance (rated on scale of i G. .S

* complete bl0ckiug,-to 1 0, no block- (ajcoatin -to-edaun' 10 4 9 10, i 9 omp e ts f es ve c i (b) .Ooating-to-foiln- 10 4 10 10' 10 S1 i i l tb' 1m 1 "70' a a i U a ers yweg I I. A,

'In' the above Table 'I, the bond strength was tested by f :--"-"i MQH i 2) llasgcizteri) V. V 1 a ars ywcig tions, andthen fo ld1 ng the" free end of one strip back (b) Specics -180? ,"and "applying an observedtension on'that end and (3) mertipmclsr' v I (a) Parts by weight r 0) Species;

thestripfsapart at" a co'nstant rate of 2 inches/minute. V I Ihe'bIocking resistance wastfes'ted 'byobser'ving thifdl fce Required platen temp; ill-degrees required to'pull pairsiof toil strips"apartjafterthey had fg ff ffll at I been; subjected to a pressure qf about 0.5 ,pound per g g t t (p u ds/ ch V v I li...;... .;...'s an. it:

In the above Table IV, DOP is an abbreviation of di (2 ethyl hexyl) phthalate, and Santicizer is o-cresyl p-toluene sulfonate sold by Monsanto Chemical Co., St. Louis, M0. The other designations have been described above.

While I have described present preferred embodiments of the invention and methods of practicing the same, it will be recognized that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

I claim:

1. A process of bonding metal foil, comprising the steps of providing metal foil coated with an adhesive composition resistant to premature bonding, and subsequently superimposing pieces of foil with said coating therebetween and bonding them together by the application of heat and pressure, said adhesive composition having (1) a resin component, (2) a plasticizer component, and (3) a component of inert particles, said resin component (1) consisting of a first material comprising solvent-soluble copolymers of a vinyl halide, a vinyl ester of a lower saturated fatty acid, and an aliphatic alpha, beta-mono-olefinic carboxylic acid, the amount of carboXylic acid combined in the copolymer being between about 0.1% and about 4% by weight of the polymer and the carboxyl groups in the polymer being substantially unreacted, said first material constituting about 50% to 100% by weight of the resin component (1), the balance of resin component 1) being a vinyl polymeric material compatible with said first material as evidenced by clarity of a solution of a mixture of said materials; said plasticizer component (2) consisting of a plasticizer for the resin component (1) which has a boiling point above 200 C., and is fluid at about 25 C., and said component (3) consisting of small discrete particles of silica aerogel which is not chemically or physically altered by intermixture with the other two components, the proportion by weight of the resin component being 60% to 80% of the combined weight of the resin and plasticizer components (1) and (2), the balance of said combined weight being the plasticizer component (2), and the proportion of the said component (3) being 1% to 20% of the combined weight of the said components (1), (2) and (3).

2. The process of claim 1 in which the said first material in the resin component (1) consists of a copolymer of vinyl chloride, vinyl acetate, and maleic acid.

3. The process of claim 1 in which the said first material in the resin component 1) consists of a copolymer of vinyl chloride, vinyl acetate and maleic acid, in proportions by weight in the copolymer of about 86%, about 13% and about 1%, respectively.

4. The process of claim 1 in which the plasticizer component (2) is a hydrocarbon ester of an acid selected from the group consisting of adipic acid, sebacic acid, sulfonic acid and mixtures thereof.

5. The process of claim 1 in which the plasticizer component (2) consists of di (2 ethyl hexyl) phthalate.

6. The process of claim 1 in which the foil is aluminum.

7. A process of bonding aluminum foil, comprising the steps of providing aluminum foil coated with an adhesive composition resistant to premature bonding, and subsequently superimposing pieces of said foil with said coating therebetween and applying a pressure of 20 to 60 pounds per square inch at 150 to 500 F. for a quarter of a second to ten seconds to bond the superimposed pieces of foil together, said adhesive composition having (1) a resin component, (2) a plasticizer component, and (3) a component of inert particles, said resin component (1) consisting of a solvent-soluble copolymer of vinyl chloride, vinyl acetate and maleic acid in proportions by weight of about 86%, 13% and 1%, respectively; said plasticizer component (2) consisting of di (2 ethyl hexyl) phthalate; and said component (3) consisting of small discrete particles of silica aerogel which is not chemically or physically altered by mixture with the other two components, the proportion by weight of the resin component (1) being 60% to of the combined weight of the resin and plasticizer components (1) and (2), the balance of said combined weight being the plasticizer component (2), and the proportion of the said component (3) being 1% to 20% of the combined weight of the components (1), (2) and (3).

8. Metal foil coated with an adhesive composition resistant to premature bonding, and adapted to permit pieces of coated foil to be superimposed with said coating therebetween and bonded together by the application of heat and pressure, said adhesive composition having (1) a resin component, (2) a plasticizer component, and (3) a component of inert particles, said resin component (1) consisting of a first material comprising solvent soluble copolymers of a vinyl halide, a vinyl ester of a lower saturated fatty acid, and an aliphatic alpha, beta-monoolefinic carboxylic acid, the amount of carboxylic acid combined in the copolymer being between about 0.1% and about 4% by weight of the polymer and the carboxyl groups in the polymer being substantially unreacted, said first material constituting about 50% to by weight of the resin component (1), the balance of resin component (1) being a vinyl polymeric material compatible with said first material as evidenced by clarity of a solution of a mixture of said materials; said plasticizer component (2) consisting of a plasticizer for the resin component (1) which has a boiling point above 200 C., and is fluid at about 25 C., and said component (3) consisting of small discrete particles of silica aerogel which is not chemically or physically altered by intermixture with the other two components, the proportion by weight of the resin component being 60% to 80% of the combined weight of the resin and plasticizer components (1) and (2), the balance of said combined weight being the plasticizer component (2), and the proportion of the said component (3) being 1% to 20% of the combined weight of the said components (1), (2) and (3).

9. Coated foil as recited in claim 8 in which said metal foil is aluminum foil.

References Cited in the file of this patent UNITED STATES PATENTS 2,149,732 Golf Mar. 7, 1939 2,329,456 Campbell Sept. 14, 1943 2,423,870 Blessing July 15, 1947 2,427,513 Spessard Sept. 16, 1947 2,467,340 Seymour Apr. 12, 1949 2,676,943 Carson Apr. 27, 1954 2,708,289 Collings May 17, 1955 OTHER REFERENCES Plasticizers, by D. H. Buttrey, published by Cleaver- Hume Press Ltd., London, 1950, page 107. 

1. A PROCESS OF BONDING METAL FOIL, COMPRISING THE STEPS OF PROVIDING METAL FOIL COATED WITH AN ADHESIVE COMPOSITION RESISTANT TO PREMATURE BONDING, AND SUBSEQUENTLY SUPERIMPOSING PIECES OF FOIL WITH SAID COATING THEREBETWEEN AND BONDING THEM TOGETHER BY THE APPLICATION OF HEAT AND PRESSURE, SAID ADHESIVE COMPOSITION HAVING (1) A RESIN COMPONENT, (2) A PLASTICIZER COMPONENT, AND (3) A COMPONENT OF INERT PARTICLES, SAID RESIN COMPONENT (1) CONSISTING OF A FIRST MATERIAL COMPRISING SOLVENT-SOLUBLE COPOLYMERS OF A VINYL HALIDE, A VINYL ESTER OF A LOWER SATURATED FATTY ACID, AND AN ALIPHATIC ALPHA, BETA-MONO-OLEFINIC CARBOXYLIC ACID, THE AMOUNT OF CARBOXYLIC ACID COMBINED IN THE COPOLYMER BEING BETWEEN ABOUT 0.1% AND ABOUT 4% BY WEIGHT OF THE POLYMER AND THE CARBOXYL GROUPS IN THE POLYMER BEING SUBSTANTIALLY UNREACTED, SAID FIRST MATERIAL CONSTITUTING ABOUT 50% TO 100% BY WEIGHT OF THE RESIN COMPONENT (1), THE BALANCE OF RESIN COMPONENT (1) BEING A VINYL POLYMERIC MATERIAL COMPATIBLE WITH SAID FIRST MATERIAL AS EVIDENCED BY CLARITY OF A SOLUTION OF A MIXTURE OF SAID MATERIALS, SAID PLASTICIZER COMPONENT (2) CONSISTING OF A PLASTICIZER FOR THE RESIN COMPONENT (1) WHICH HAS A BOILING POINT ABOVE 200*C., AND IS FLUID AT ABOUT 25*C., AND SAID COMPONENT (3) CONSISTING OF SMALL DISCRETE PARTICLES OF SILICA AEROGEL WHICH IS NOT CHEMICALLY OR PHYSICALLY ALTERED BY INTERMIXTURE WITH THE OTHER TWO COMPONENTS, THE PROPORTION BY WEIGHT OF THE RESIN COMPONENT BEING 60% TO 80% OF THE COMBINED WEIGHT OF THE RESIN AND PLASTICIZER COMPONENTS (1) AND (2), THE BALANCE OF SAID COMBINED WEIGHT BEING THE PLASTICIZER COMPONENT (2), AND THE PROPORTION OF THE SAID COMPONENT (3) BEING 1% TO 20% OF THE COMBINED WEIGHT OF THE SAID COMPONENTS (1), (2) AND (3). 